Semiconductor module having a solder-bonded cooling unit

Abstract

A semiconductor module including an insulated circuit substrate having a substrate, a circuit layer on a front surface of the substrate, and a metal layer on a back surface of the substrate; a semiconductor element electrically connected to the circuit layer; a cooling unit having a ceiling board bonded to the metal layer, a bottom board opposite the ceiling board, a side wall connecting a periphery of the ceiling board and a periphery of the bottom board, and a fin connecting the ceiling board and bottom board, where thickness of the ceiling board is at least 0.5 mm and at most 2.0 mm and total thickness of the ceiling board and bottom board is at least 3 mm and at most 6 mm; and a solder layer that bonds together the metal layer and the ceiling board by melting at a temperature of at least 200° C. and at most 350° C.

What is claimed is: 
     
       1. A semiconductor module comprising:
 an insulated circuit substrate that includes a substrate, a circuit layer arranged on a front surface of the substrate, and a metal layer arranged on a back surface of the substrate; 
 a semiconductor element that is electrically connected to the circuit layer; 
 a cooling unit that includes a ceiling board with a uniform thickness and a flat surface bonded to the metal layer, a bottom board arranged opposite the ceiling board, a side wall that connects a periphery of the ceiling board and a periphery of the bottom board, and a fin that connects the ceiling board and the bottom board, where the thickness of the ceiling board is greater than or equal to 0.5 mm and less than or equal to 2.0 mm and a total thickness of the ceiling board and the bottom board is greater than or equal to 3 mm and less than or equal to 4 mm; and 
 a solder bonding layer that bonds an entire back surface of the metal layer to the ceiling board, the solder bonding layer having a functional melt temperature of less than or equal to 350° C., said solder bonding layer not melting below 200° C.; 
 wherein a thickness of the bottom board is greater than or equal to two times the thickness of the ceiling board and less than three times the thickness of the ceiling board. 
 
     
     
       2. The semiconductor module according to  claim 1 , wherein
 the bottom board is thicker than the ceiling board. 
 
     
     
       3. The semiconductor module according to  claim 1 , wherein
 thickness of the bottom board is greater than or equal to the thickness of the ceiling board and less than or equal to five times the thickness of the ceiling board. 
 
     
     
       4. The semiconductor module according to  claim 1 , wherein
 the side wall is formed integrally with the bottom board, and 
 the semiconductor module further comprises bonding members that connect the ceiling board and the side wall, connect the ceiling board and the fin, connect the bottom board and the fin, and enter a melted state at the same temperature as the solder layer. 
 
     
     
       5. The semiconductor module according to  claim 1 , wherein
 material of the ceiling board and the bottom board is aluminum or an aluminum alloy. 
 
     
     
       6. The semiconductor module according to  claim 5 , wherein
 the cooling unit is formed by integrally molding the ceiling board, the bottom board, the side wall, and the fin. 
 
     
     
       7. The semiconductor module according to  claim 5 , wherein
 the cooling unit is formed by integrally bonding a composite member that is the bottom board and the side wall formed integrally, the ceiling board, and the fin with a bonding member. 
 
     
     
       8. The semiconductor module according to  claim 4 , wherein the bonding members and the solder bonding layer have a same composition.